Conventionally, in an image forming apparatus using an electrophotographic image forming process, a photosensitive drum and process parts actable on the photosensitive drum are not fixed to the appartus, but rather are provided in a cartridge, for example, as a process cartridge that is detachably mountable to an apparatus main assembly of the image forming apparatus.
With this type of process cartridge, maintenance of the image forming apparatus can be performed by a user himself (herself). As a result, operaiton of the apparatus is improved, and, thus process cartridges are widely used in image forming apparatuses.
In a full-color electrophotographic image forming apparatus using a transfer belt (intermediary transfer belt), a constitution is used in which a plurality of process cartridges are arranged below the transfer belt. This is because in the case in which a print is discharged onto an upper surface of the image forming apparatus, by positioning the process cartridges below the transfer belt, the time to a first printing can be shortened. As a process cartridge corresponding to this constitution, an arrangement is used in which a developing chamber is disposed at an upper portion close to the transfer belt and developer is scooped up, to the developing chamber, from a developer accommodating chamber positioned below the developing chamber (Japanese Laid-Open Patent Application 2008-170951).
In this process cartridge, by providing a stirring member in the developing chamber, circulation of the developer in the developing chamber is improved, so that the developer is efficiently supplied to the developing roller above the developing chamber so as to reduce an amount of residual developer.
However, in the constitution of Japanese Laid-Open Patent Application 2008-170951, there was a need to provide the stirring member in the developing chamber at a side below a contact portion between a developing roller and a developer supplying roller in the developing chamber. Therefore, the developer supplying roller for supplying the developer to the developing roller is rotated in a rotational direction opposite to rotational direction of the developing roller, so that circulation of the developer is made equivalent to or more than a conventional level without providing the stirring member in the developing chamber, and a supplying property of the developer from the developer supplying roller to the developing roller can be satisfied. According to this constitution, a space conventionally used for disposing the stirring member can be filled, and therefore residual developer can be further suppressed.
The present invention is a further development of the prior art structure.